In the output of show ip interface brief, what is the default state of router interfaces?

The default state of router interfaces in the output of the command "show ip interface brief" is administratively down/down. When an interface is first created or when it is not explicitly activated, its status is set to administratively down. This means that the interface has not been enabled by the network administrator.

In practical terms, administratively down indicates that the interface is disabled through configuration (typically using the "shutdown" command). Until the administrator issues the command to "no shutdown," the interface will remain in this state, indicating that it is not operational.

The interface may be physically present (hardware-wise), but it cannot send or receive any packets until it is administratively activated. Understanding this default state is crucial for troubleshooting and configuring router interfaces effectively.